1. Field of the Invention
The present invention relates to a purification technique for process surfaces from substrates to semiconductor devices, surfaces of process apparatus and process apparatus parts, and surfaces of apparatus and apparatus parts in relation to lithographic processes, in manufacturing processes of semiconductor devices and liquid crystal display devices, particularly to an innovative technique for surface purification by xe2x80x9cprecise cleaning action of steam and ultraviolet raysxe2x80x9d, and breakaway from a resources/energy high-consumption type technique, that is, a development of an environment-symbiosis type technique which makes dependence upon chemical substances minimum.
2. Description of the Related Art
A very minute process surface cleaning technique in manufacturing a semiconductor device or a liquid crystal display device, depends on a multi-stage process in which a large quantity of ultrapure water and various kinds of chemicals are used in a large-sized apparatus called wet cleaning system. As a technique for renovating this, a cleaning technique using a one-by-one cleaning system is also promoted.
But, these cleaning techniques have not entirely reached the satisfactory level in breakaway from a load of cleaning process and burdens of ultrapure water and chemicals, and following to performance development demand.
In a cleaning technique in a general industrial field, xe2x80x9cfluid jet methodxe2x80x9d is a generally used method. Cleaningxe2x80x94surface-peelingxe2x80x94surface-polishing are possible by a particulate fluid (ice particulates/abrasive particulates) entrained on a jet flow of a high-pressure fluid. It is generally used in case of a large size such as aircraft/vehicles and requiring on-the-spot cleaning. Cleaning methods of spraying steam are also well known, and used for cleaning not only in industrial fields but also in medical/food fields and homes. But, as described later, there is a great difference between the cleaning level in these fields and a required level in a manufacturing field of semiconductor devices or liquid crystal display devices.
Manufacturing process of semiconductor devices/liquid crystal display devices differs from other fields in the feature that it is consistently surface-processing process. It has the technical feature that a surface purification technique affects the performance of products. It is a special field wherein purification levels of all surfaces of not only process surfaces from substrates to semiconductor devices, but also surfaces of process apparatus and process apparatus parts as a matter of course, to surfaces of apparatus and apparatus parts in relation to lithographic processes, become severer with progress of technical generations.
Surfaces to deal with in the present invention are as follows: such as surfaces of silicon substrates/glass substrates/chemical mechanical polishing (CMP) substrates/lithographic process substrates/wiring substrates as process surfaces from substrates to semiconductor devices; such as surfaces of ion-implantation apparatus/plasma apparatus/CVD apparatus and their apparatus parts as surfaces of process apparatus and process apparatus parts; and such as surfaces of stepper devices and mask reticles as surfaces of apparatus and apparatus parts in relation to lithographic processes.
The present inventors perceive the principle of surface purification by steam and ultraviolet rays. And, not xe2x80x9cCleaningxe2x80x9d but xe2x80x9cPurificationxe2x80x9d is intended. This is because the purification degree in a general cleaning technique and the purification required degree in a manufacturing field of a semiconductor device or a liquid crystal display device are quiet different in level. Table 1 shows the difference in surface purification degree level.
In general, cleaning is a technique from the level {circumflex over (1)} to the level {circumflex over (2)}. For example, in a metal material surface, the roughness of the mechanical polishing surface is scores xcexcm, and mechanical processing oil is adhering at a level of several mg/cm2. Even in case that the surface roughness is decreased to about 10 xcexcm by chemical polishing surface, it is adhering at a level of 1 mg/cm2. The cleaning object is attained when the contamination is removed by about three figures starting from this level {circumflex over (1)} to reach the level {circumflex over (2)}. In a general industrial field, this surface may be considered to be pure.
On the other hand, in semiconductor/liquid crystal industries, the level {circumflex over (2)} is the starting point. Present of contaminant molecules in several molecular layers means that molecules/atoms of the substrate are not present in the surface. It defeats its own purpose of making the surface function. Purification is a technique in which the contamination is decreased from the level by about three figures to reach the level {circumflex over (3)}. Even in this case, a problem may yet remain in the surface operation mechanism in accordance with the kind of contaminant molecules. In the future ultra-LSI generation, the level {circumflex over (4)} (10xe2x88x926 to 10xe2x88x927 molecular layers) is required which is lower by about four figures than the level {circumflex over (3)}.
It is an object of the present invention to provide a surface purification apparatus and a surface purification method capable of xe2x80x9cprecisely cleaningxe2x80x9d a surface into the molecular/atomic level and making the purification degree of the surface 1012 molecules/cm2 or less, by a new principle and apparatus. In this specification, xe2x80x9cPrecise Cleaningxe2x80x9d of a surface at the molecular/atomic level is expressed by the term of xe2x80x9cPurificationxe2x80x9d.
In order to attain the above object, a surface purification apparatus of the present invention is an apparatus used in a manufacturing process of a semiconductor device or a liquid crystal display device, comprising means for bringing steam into contact with and means for spraying steam onto a surface having need of purification, wherein said surface is purified.
In an aspect of the surface purification apparatus of the present invention, said surface is one selected from among process surfaces from a substrate to a semiconductor device, surfaces of process apparatus and process apparatus parts, and surfaces of apparatus and apparatus parts in relation to lithographic processes.
In an aspect of the surface purification apparatus of the present invention, said surface is processed with saturated or superheated steam at a temperature of 70xc2x0 C. to 200xc2x0 C.
An aspect of the surface purification apparatus of the present invention, comprises a steam supply apparatus comprising a steam generation system, a steam-superheating system, a control system for supplied ultrapure-water quantity and heat amount, and a steam pressure control system, constructed with including a steam inlet and steam-spraying nozzle, and arbitrarily switching and supplying saturated or superheated steam at a temperature of 70xc2x0 C. to 200xc2x0 C.
In an aspect of the surface purification apparatus of the present invention, said steam supply apparatus further includes a switching system for a supply line for a solution containing a purification promotion ingredient and said ultrapure water supply line, and an injection pump, and comprises a system for switching steam containing said purification promotion ingredient and steam not containing it.
An aspect of the surface purification apparatus of the present invention, comprises irradiation means for irradiating with ultraviolet rays, wherein said surface is processed in combination with processing of irradiating said surface with ultraviolet rays in said steam processing.
In an aspect of the surface purification apparatus of the present invention, said irradiation means uses an ultraviolet lamp of a wavelength corresponding to a 50% transmissive distance of not less than 10 mm to steam.
In a surface purification apparatus of the present invention, a system for introducing steam, and a drive system in which a spraying surface is swept by a steam-spraying nozzle moving relatively to a surface being processed, are provided in a chamber including a substrate take in/out system and an atmosphere discharge system, and said steam-spraying nozzle sprays steam onto said surface.
In an aspect of the surface purification apparatus of the present invention, an ultraviolet reactor comprising an ultraviolet lamp of a wavelength corresponding to a 50% transmissive distance of not less than 10 mm to steam, is accompanied, said ultraviolet lamp is disposed in parallel with said surface, and said surface in steam processing is irradiated and processed.
In an aspect of the surface purification apparatus of the present invention, said atmosphere discharge system further comprises a suction system, and the surface being processed is dried by discharging the atmosphere in the chamber after superheated steam processing.
A surface purification method of the present invention is a method used in a manufacturing process of a semiconductor device or a liquid crystal display device, wherein, by using a process for bringing steam into contact with a surface having need of purification, and a process for spraying steam onto the surface having need of purification, said surface is processed.
In an aspect of the surface purification method of the present invention, said surface is one selected from among process surfaces from a substrate to a semiconductor device, surfaces of process apparatus and process apparatus parts, and surfaces of apparatus and apparatus parts in relation to lithographic processes.
In an aspect of the surface purification method of the present invention, said surface is processed with saturated or superheated steam at a temperature of 70xc2x0 C. to 200xc2x0 C.
In an aspect of the surface purification method of the present invention, said surface is processed in combination with processing of irradiating said surface with ultraviolet rays of a wavelength corresponding to a 50% transmissive distance of not less than 10 mm to steam, in said steam processing.
In an aspect of the surface purification method of the present invention, organic matters having adhered to said surface are removed by said steam processing and said process of irradiating with ultraviolet rays.
In an aspect of the surface purification method of the present invention, an organic matter film formed on said surface is removed by said steam processing and said process of irradiating with ultraviolet rays.
In an aspect of the surface purification method of the present invention, particles having adhered to said surface are removed by said steam processing and said process of irradiating with ultraviolet rays.
In an aspect of the surface purification method of the present invention, generation of water marks is staved off by discharging the atmosphere in the chamber after superheated steam processing of said surface, and drying the surface being processed.
In an aspect of the surface purification method of the present invention, said surface is a silicon substrate, and said silicon surface is made to be a hydrogen termination structure by steam-processing silicon exposed on said silicon substrate surface.